In heat assisted magnetic recording (HAMR), information bits are recorded on a data storage medium at elevated temperatures, and the data bit dimension can be determined by the dimensions of the heated area in the storage medium or the dimensions of an area of the storage medium that is subjected to a magnetic field. In one approach, a beam of light is condensed to a small optical spot onto the storage medium to heat a portion of the medium and reduce the magnetic coercivity of the heated portion. Data is then written to the reduced coercivity region. Heat assisted magnetic recording is also referred to a thermally assisted magnetic recording.
Current HAMR recording head designs generally have a near field transducer (NFT) that is capable of focusing light to a spot size smaller than the diffraction limit. The NFT is designed to reach local surface-plasmon when subjected to light at a particular wavelength. At resonance, a high electric field surrounding the NFT appears, due to the collective oscillation of electrons in the metal. A portion of the field will tunnel into the storage medium and get absorbed, raising the temperature of the medium locally for recording. To help dissipate the heat, a heat sink can be added to the NFT.
It would be desirable to confine the light to a region under the near field transducer at the air bearing surface.